As the frequency of operation of a magnetic component such as an inductor or transformer increases, the depth to which current penetrates the transformer's conductors decreases. This penetration depth is referred to as the "skin depth". At room temperature, copper has a skin depth .delta. equal to 2.60.sqroot.1/f where f is in Hertz. Thus, at a frequency of about 1 megahertz, the current penetration in copper is only on the order of 2.6 mils. Consequently, if the conductors are more than several skin depths thick, then any portion of the conductors which is further than 3.delta. from the exterior surface is not involved in carrying the inductor or transformer currents. For high frequency operation, magnetic components are made as small as possible and, therefore, inactive conductive material adds to the weight and volume of the component without enhancing its operational characteristics. Consequently, for high frequency magnetic components, it has become commonplace to use a planar conductive film having a thickness on the order of twice the skin depth at the intended operating frequency as the magnetic component's conductors. These conductive films are normally disposed on a dielectric membrane and patterned to provide the desired winding configuration. Multi-turn windings normally comprise either a single layer spiral or a stack of layers of individual conductive films on dielectric substrates which are interconnected layer-to-layer with soldered connecting bars to provide a continuous winding. Spiral windings are limited in the number of turns they can provide for high currents and multilayer windings have the disadvantage of requiring a number of layer-to-layer connections which increases with the number of turns in a winding. Connecting thin conductive layers layer-to-layer with connecting bars which are soldered to the edge of a conductor is an exacting process which tends to have a poor yield since the solder can easily short out layers or fail to connect to a layer, which results in an inoperative winding.
Consequently, there is a need both for an improved method of fabricating multi-turn, multilayer thin film magnetic windings and for an improved structure which ensures good operating characteristics and which is easily fabricated.